1. Field of the Invention
The present invention relates to capacitor charging semiconductor apparatuses, in particular, to capacitor charging semiconductor apparatuses each integrally formed from a plurality of parallel monitor circuits to equally charge a plurality of electric double layer type capacitors, which are serially connected to each other.
2. Discussion of the Background Art
An electric double layer type capacitor can be charged faster than a secondary battery because the secondary battery generally takes a certain time period to be charged. Since a rated voltage of the electric double layer type capacitor is generally low, for example, approximately three volts, a necessary voltage is typically obtained by serially connecting a plurality of such capacitors. When charging such capacitors, a problem that arises is unevenness of charge caused by a difference in a capacitor capacitance, its own charging and discharging, and so on. One approach is to employ an equally charging circuit called a parallel monitor circuit as illustrated in FIG. 6. Specifically, since an output of a comparator CMP1 becomes high, and accordingly a transistor Tr1 is turned on when a voltage V1 of a capacitor C1 exceeds a reference voltage Vr1 in the parallel monitor circuit, charge current is bypassed by the transistor Tr1 to avoid excessive charging to the capacitor C1 as discussed in Japanese Patent Application Laid Open No. 2000-50495, for example.
However, due to non-integration of a semiconductor apparatus, i.e., assembly of discrete parts, size and cost of the background parallel monitor circuit increase. Then, the integration is conventionally demanded. However, if a semiconductor apparatus is manufactured while changing a number of parallel monitor circuits to be integrated, a small number of various products are generally produced because the number of serially connected capacitors varies depending upon usage. As a result, advantages of mass-production of the semiconductor apparatus are suppressed. Thus, the semiconductor apparatus is expensive and cannot practically be used. Further, if a semiconductor apparatus is manufactured with it being integrated with only one parallel monitor circuit, the parallel monitor circuit cannot be effectively downsized resulting in loss of the advantages of the integration.
Then, as shown in FIG. 1, when approximately five to ten parallel monitor circuits (e.g. five in FIG. 1) are integrated on one semiconductor apparatus IC1, and a number of capacitors to be charged is more than that of the integrated parallel monitor circuits, the same semiconductor apparatuses can be longitudinally connected as needed. Thus, a semiconductor apparatus can be mass-produced, while downsizing and reducing cost of the entire monitor circuit.
However, a total number of chargeable capacitors are unavoidably integral multiples of that of capacitors charged by one semiconductor apparatus. As a result, the other number of capacitors cannot be charged.